Near field communication (NFC) is a set of standards for smartphones and similar devices utilized to establish radio communication between two devices by touching them together or bringing them into proximity, typically at a distance of 10 cm or less.
NFC uses electromagnetic induction between two loop antennas located within each other's near field, effectively forming an air-core transformer. It operates within globally available and unlicensed radio frequency bands, such as 13.56 MHz, and at rates ranging from 106 kbit/s to 424 kbit/s. NFC involves an initiator and a target; the initiator actively generates an RF field that can power a passive target, an unpowered chip called a “tag”. This enables NFC targets to take simple form factors such as stickers, key fobs, or cards that do not use batteries.
NFC tags store data (typically between 96 and 4,096 bytes) and may be read-only, but may alternatively be rewriteable. The tags can securely store personal data such as debit and credit card information, loyalty program data, personal identification numbers, and networking contacts, among other information. They can be custom-encoded by their manufacturers or use the specifications provided by the NFC Forum, an industry association.
In addition to communication between a powered NFC device and an unpowered NFC device, NFC peer-to-peer communication is possible, provided both devices are powered. This may be utilized for data peer-to-peer data transfers, for example. In addition, an active NFC device may emulate an NFC card in what is called a card emulation mode.
In an NFC communication between an NFC tag and an active NFC device, or between a powered NFC device in card emulation mode and an active NFC device, there is an initialization period. As per the ISO 14443 standard for such communications, the NFC tag or powered NFC device in card emulation mode is to respond to lower level protocol commands within a given period of time from application of an unmodulated electric field by the active NFC device. In order to respond to those commands, provided there is no non-volatile memory available, the NFC tag or powered NFC device in card emulation mode first loads configuration data, and then responds to those commands based upon the configuration data. Therefore, the NFC tag or powered NFC device in card emulation mode is preferably able to load the configuration data and respond to the commands in the given period of time.
While certain configurations wherein the NFC tag or powered NFC device in card emulation mode are able to load the configuration data within the given period of time are known, additional configurations may be desirable. Therefore, new methods of handling data during the initialization period are desired.